I have done the main quest several times. On this character, when I am asked to demonstrate my shout, the Greybeards go nuts on me after I use unrelenting force. Once I was able to stay alive long enough to yield, and when Einarth showed me the next word in unrelenting force and I was supposed to shout at the apparitions that appear, they all went nuts and attacked me again.

I am on PC, and I have all three DLCs.

Help?

Are you using Unrelenting Force...

...at them?

Do you have any mods that might increase their aggression or something?

Yes. As I said, I have done this many times. I have been playing since launch. I am not that much of a noob.

I have the Deadly Combat mod, but I can't see that doing anything. Plus I have used it with two other characters and it was fine.

Does that mod, or anything else edit unrelenting force? It could be making it "hostile" or "painful" or something that making the Greybeards react. Akin to throwing a fireball at them or something.

do you have Dragonborn Force (active effect from DB DLC)

maybe DB force + Deadly Combat mod = Greybeards going Crayzaaay

Let me guess, you killed their leader?

I always blast it right at them. I briefly see their life bar, like when you start fighting a real enemy, but then they go back to being normal.

So, it must be scripted for them to immediately stop combat after being hit with that shout. So, that would be the place to look for conflicts with other mods.